1. Field
The present invention relates to a semiconductor device, and more specifically, to a light emitting diode (LED).
2. Discussion of the Background
A light emitting diode (LED) is a device including an n-type semiconductor layer, a p-type semiconductor layer, and an active layer disposed between the n-type semiconductor layer and the p-type semiconductor layer. When a forward electric field is applied to the n-type and p-type semiconductor layers, electrons and holes are injected into the active layer, and the electrons and holes injected into the active layer are recombined to emit light.
Efficiency of the LED may depend on internal quantum efficiency and external quantum efficiency known as light extraction efficiency. In order to increase the light extraction efficiency, there is a method in which a concavo-convex pattern is formed on a substrate, for example, a patterned sapphire substrate (PSS), and then a semiconductor layer is grown on the concavo-convex pattern. However, the light extraction efficiency may still remain low.
As another method of increasing the light extraction efficiency, Korean Patent Publication No. 2012-0083740 discloses the formation of a concavo-convex pattern on an upper surface of an LED.